Conventionally, as means for displaying a three-dimensional image based on information on the three-dimensional image and allowing an observer to recognize the three-dimensional image, there were known a naked-eye stereoscopic paralleling method in which a right image of two images having a binocular parallax is viewed with a right eye and a left image is viewed with a left eye, a stereoscope method in which an image is viewed using a pair of spectacles fitted with a liquid shutter or using different lenses for the right eye and the left eye, an anaglyph method in which a binocular parallax image having different colors of red and blue is viewed with red-blue spectacles. However, wearing special spectacles or training an observer is required for the observer to view a three-dimensional image using the above-mentioned methods.
In recent years, with development of a liquid crystal technology, liquid crystal monitors capable of displaying an image without using special spectacles were introduced to the market. Most of the liquid crystal monitors are three-dimensional liquid crystal display apparatuses of an image splitter type without spectacles, that is, three-dimensional image display apparatuses of a so-called parallax barrier type or a lenticular lens type having only a horizontal parallax.
In the three-dimensional image display apparatuses of a parallax barrier type or a lenticular lens type, the appearance of solidity is created by spatially forming optical image paths so that a right-eye image is viewed at a right-eye position and a left-eye image is viewed at a left-eye position. Accordingly, since the optical image path is spatially and periodically formed at the right-eye position and the left-eye position, the appearance of solidity is deteriorated when the optical image paths depart from the fixed positions. In addition, since images having a horizontal parallax are formed in principle, the appearance of solidity is deteriorated when the right-eye position and the left-eye position depart from the horizontal direction. Therefore, when it is intended to carry out stereoscopic views while maintaining the appearance of solidity of a three-dimensional video for a long time, it is necessary to fix the right-eye position and the left-eye position to predetermined positions in space, respectively.
As for the horizontal dislocation of the right-eye position and the left-eye position, there has been suggested a method of specifying positions of an observer's eyes or a position of the observer's face with a sensor and controlling and correcting the optical image path in accordance with the dislocation of the specified position. However, in this case, there is a problem that the apparatus increases in size and thus markers should be attached to the observer so as to sense the positions of the eyes or the position of the face.
By advancing the integral photography suggested by M. G. Lipmann in 1908 in order to solve the above-mentioned problems, there was recently suggested a three-dimensional image display method using a two-dimensional display panel such as a liquid crystal panel and a pin-hole or fly-eye lens array instead of a film (for example, see Japanese Unexamined Patent Application Publication No. 2001-275134).
In the integral photography suggested by M. G. Lipmann, a film is disposed at a focal position of a fly-eye convex lens array and images of the fly-eye convex lenses are recorded on the surface of the film. At the time of reproducing the recorded images, the images of the fly-eye convex lenses recorded on the film are reproduced into a stereoscopic image by the use of the same fly-eye convex lens array as photographing the stereoscopic image.
In order to smoothly display a three-dimensional image with a high resolution by the use of the integral photography, it is necessary to dispose different parallax images in the pinholes or lenses having a small diameter. Here, the two-dimensional resolution of the appearance depends upon the lens diameter of the pinhole or lens array. However, since the image information on the three-dimensional image of the appearance also relates to a density of the image formed in the depth direction, the image information on the three-dimensional image of the appearance does not depend upon only the lens diameter of the two-dimensional pinhole or lens array. However, when a human being views a three-dimensional image and the profile of the lens is clear, decrease in resolution occurs due to recognition of the size of the profile.
In the integral photography method or the ray reproducing method, since a convex lens array or a pinhole array made of glass or resin is used as means for forming a two-dimensional image including parallax images in a space, the profile of the lens is clear, thereby decreasing the two-dimensional resolution. The integral photography method was embodied using a lenticular lens array, but the two-dimensional resolution was decreased due to vertical stripe profiles of the lenticular lenses.
When a three-dimensional image is displayed using the fly-eye lens array, the lenticular lens array, or the pinhole array, crosstalk occurs in the neighboring lenses or pinholes at the time of forming an image corresponding to display data to be displayed in a two-dimensional display unit. Accordingly, there was an attempt to reduce the crosstalk by making it difficult to form the image corresponding to the display data in the geometrically neighboring lenses by the use of lenses with a short focal length. In order to embody the short focal length with an optical system having a simple structure, it is advantageous to reduce the radius of curvature of the lenses, but it is very difficult to efficiently manufacture a lens array having a small radius of curvature. In addition, there was an attempt to optically isolate the lenses one by one by the use of a light blocking mask, but there is a problem that the reproduced three-dimensional image becomes dark and the reproduction of the three-dimensional image is hindered due to the profile of the light blocking mask.